Thursday, April 20, 2006

The House Crow and the bat

The House Crow and the bat

On 19th April 2006 we had a posting by Angie Ng about how a House Crow (Corvus splendens) attacked and surgically cut up a rat. Gloria Seow, a member of the Nature Society (Singapore), read the account and sent in her encounter of these crows with an unfortunate bat.

“I am a member of NSS and I've been following your blog closely. Very interesting read so far, good job!

“Anyhow, since the topic has turned to crows and their hunting instincts, I am compelled to relate an encounter that I had with them. I was cycling through a quiet street flanked by landed properties on both sides (in Singapore) when I spied a group of about 6 House Crows in the middle of the street, pecking furiously at something. I stopped my bike out of curiosity and as I walked over to see what the commotion was about, the crows flew off en masse, unveiling their victim - a small bat that looked next to dead.

“The crows were apparently pecking at the bat's throat, which was mangled and bloodied. There was nothing I could do to help the poor bat, which I believe had been systematically hunted by the crows. My theory is that it was probably napping in the mango tree (the incident happend at around 11am) when the crows decided that it was going to be their next meal.

“After snapping a few shots of the bat with my camera phone, I had to step aside for a passing car, and when I returned, the bat had apparently reared itself into a L-shaped 'sitting' position, when previously it was lying flat on the tarmac. It was probably reacting to the prospect of being crushed by the passing vehicle.

“I did not stay to watch the crows finish off the little bat, which I'm sure would have been what happened after I left.

“I'm not surprised that crows are hunters too, given their advantage of having a larger built than most other birds, their huge beaks and their sheer numbers. The explosion of the crow population in Singapore also points to the abundance of food sources, which I'm sure cannot be just due to the rubbish left lying around, after all, Singapore is supposed to be CLEAN and green.

Warmest regards, Gloria Seow”

Our bird specialais, R. Subaraj has this to say: The bat in the photos appears to be a Common Fruit Bat (or Lesser Short-nosed Fruit Bat), Cynopterus brachyotis. This is quite possibly our commonest local bat and is widespread in all habitats. They are often the colony found roosting under palm fronds or epiphytic ferns.

The crows are efficient hunters, though scavenging where ever possible is much easier. There are many accounts of crows attacking and killing a variety of animals, though more often than not, they would target the old, sick, weak or young.

The House Crow is the introduced species found commonly throughout most of Singapore, particularly around the more urbanised areas. It is largely a scavenger but is also a true opportunist. Often, when some birds like herons nest communally, the crows will take up residence nearby and steal eggs and chicks when the adults leave the nests unguarded. As a result, the large populations that exists in parts of Singapore pose a real threat to native bird populations. The fairly recent colonisation of Asian Koels (Eudynamys scolopacea) provides the first known biological control in Singapore for this feral species.

The native crow of Singapore is the Large-billed Crow (Corvus macrorhynchos). This is a much larger species and is all black without the grey on the neck that the House Crow pocesses. It has an impressive bill and a prominent bump on the head. It is also different in call and flight. This species is usually in pairs (unlike the flocking of the House) except when roosting for the night. They are far less common and largely occur in the less urbanised areas including our forested nature reserves. While they are proficient scavengers too, they are also effective hunters. I remember seeing a pair of Large-billed Crows chased a fruit bat, that they had probably disturbed from roost, at Khatib Bongsu some years back. Recently, I have realised that they are not above trying new things too when I watched them trying to hawk flying termites!

Thanks to Gloria Seow for the post and Subaraj for the comment. Images by Gloria.